The present invention relates to a transparent electroconductive film and a process for producing the same.
Transparent electroconductive films are used for applications such as electrodes for inorganic EL panels, liquid crystal displays and solar batteries; hot wave reflection films for window glass; and antistatic films. Among the transparent conductive films, an indium-tin oxide film comprising an indium oxide containing 2 to 20% by weight of tin oxide has many applications because of its high electroconductivity (that is, low electric resistivity) and superior translucency. The xe2x80x9cindium-tin oxidexe2x80x9d is hereinafter referred to as ITO.
However, the ITO has problems that (1) it is expensive, because it contains an expensive indium oxide in an amount of from 80 to 98% by weight, and (2) its transparency is not good, because it absorbs light ranging from visible rays having short wave lengths to ultraviolet rays.
In the production of inorganic EL panels, it is required to use a transparent electroconductive film, which does not decrease its electroconductivity even when heat-treated in air at a temperature exceeding 800xc2x0 C. However, a transparent electroconductive film comprising the ITO, which is usually used for the production of inorganic EL panels, has a problem that it decreases its electroconductivity when heat-treated under such conditions.
As one of transparent electroconductive materials substitutable for the ITO, InSbO4 is proposed. Said InSbO4 has characteristics that (1) it is cheaper than the ITO, because a content of the expensive indium oxide is only a half of that of the ITO on a weight basis, and (2) its transparency is superior to the ITO, because it absorbs little light ranging from visible rays having short wave lengths to ultraviolet rays. However, an InSbO4-containing transparent electroconductive film has never been obtained. For example, JP-A 9-71419 discloses a process for producing an InSbO4-containing sintered object comprising the steps of (i) shaping a mixed powder of an indium oxide powder and an antimony oxide powder to obtain a shaped product, and (ii) sintering the shaped product: however, it discloses no InSbO4-containing transparent electroconductive film.
An object of the present invention is to provide a process for producing an InSbO4-containing transparent eletroconductive film having a high electroconductivity and a superior transparency.
Another object of the present invention is to provide a process for producing a transparent electroconductive film exhibiting little decrease in electroconductivity even when heat-treated at a high temperature.
The present inventors have found a problem that a film obtained by sputtering a target (A) for sputtering, which target contains In, Sb and O, and whose atomic ratio of Sb/In is from 0.9 to 1.1, contains a large amount of In dramatically departing from a stoichimetric ratio of InSbO4, and as a result, a film having a high conductivity cannot be obtained.
The present inventors have undertaken extensive studies to solve such a problem, and as a result, have found that:
(1) there can be obtained an InSbO4-containing transparent electroconductive film, whose atomic ratio of In and Sb is near to the stoichimetric ratio of InSbO4 and which has a high electroconductivity, by sputtering simultaneously the above-mentioned target (A) for sputtering and a metal Sb-containing target (B) for sputtering, and
(2) there can be obtained an InSbO4-containing transparent electroconductive film, wherein Sn and/or Hf is doped, whose atomic ratio of In and Sb is near to the stoichimetric ratio of InSbO4, and which has a high electroconductivity, (a) by sputtering simultaneously the target (A) for sputtering, the target (B) for sputtering and at least one target (C) for sputtering selected from the group consisting of Sn, SnO2, Hf and HfO2; or (b) by sputtering simultaneously a target (D) for sputtering, which contains In, Sb, O and at least one element selected from the group consisting of Sn and Hf, and whose atomic ratio of Sb/In is from 0.9 to 1.1, and the target (B) for sputtering. Thereby, the present invention has been obtained.
Further, the present inventors have found that:
(1) a transparent film, which has high electroconductivity, which exhibits little decrease in electroconductivity even when heat-treated at a high temperature, and which contains In, Sb and O in a specific proportion, can be obtained by sputtering simultaneously the target (A) for sputtering and the target (B) for sputtering,
(2) a transparent film, which has high electroconductivity, which exhibits little decrease in electroconductivity even when heat-treated at a high temperature, and which contains In, Sb and O in a specific proportion, can be obtained by sputtering simultaneously the target (A) for sputtering, the target (B) for sputtering and the target (C) for sputtering,
(3) a target for sputtering, which contains In, Sb and O, and which has a specific atomic ratio of Sb/In can accomplish the objects of the present invention,
(4) a target for sputtering, which contains In, Sb, O and at least one element selected from the group consisting of Sn and Hf, and which has a specific atomic ratio of Sb/In can accomplish the objects of the present invention,
(5) there can be obtained an InSbO4-containing transparent electroconductive film by sputtering a target (E) for sputtering, which contains In, Sb and O, and which has a specific atomic ratio of Sb/In,
(6) there can be obtained an InSbO4-containing transparent electroconductive film by sputtering simultaneously the target (3) for sputtering and at least one target (C) for sputtering, and
(7) there can be obtained an InSbO4-containing transparent electroconductive film by sputtering a target (F) for sputtering, which contains In, Sb, O and at least one element selected from the group consisting Sn and Hf, and which has a specific atomic ratio of Sb/In.
Thereby, the present invention has been obtained.
The present invention provides:
(1) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering simultaneously:
(i) a target (A) for sputtering, which comprises In, Sb and O, and whose atomic ratio of Sb/In is from 0.9 to 1.1, and
(ii) a target (B) for sputtering, which comprises Sb (the process being hereinafter referred to as xe2x80x9cprocess-1xe2x80x9d),
(2) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering simultaneously:
(i) a target (A) for sputtering, which contains In, Sb and O, and whose atomic ratio of Sb/In is from 0.9 to 1.1,
(ii) a target (B) for sputtering, which contains Sb, and
(iii) at least one target (C) for sputtering selected from the group consisting of Sn, SnO2, Hf and HfO2 (the process being hereinafter referred to as xe2x80x9cprocess-2xe2x80x9d),
(3) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering simultaneously;
(i) a target CD) for sputtering, which contains In, Sb, O and at least one element selected from the group consisting of Sn and Hf, and whose atomic ratio of Sb/In Is from 0.9 to 1.1, and
(ii) a target (B) for sputtering, which contains Sb (the process being hereinafter referred to as xe2x80x9cprocess-3xe2x80x9d),
(4) a transparent eletroconductive film, which contains In, Sb and O, and whose atomic ratio of Sb/In is from 0.8 to 1.5 (the film being hereinafter referred to as xe2x80x9ctransparent electroconductive film-1xe2x80x9d),
(5) a transparent electroconductive film, which contains In, Sb, O and at least one element selected from the group consisting of Sn and Hf, and whose atomic ratio of Sb/In is from 0.8 to 1.5 (the film being hereinafter referred to as xe2x80x9ctransparent conductive film-2xe2x80x9d),
(6) a target for sputtering, which contains In, Sb and O, and whose atomic ratio of Sb/In is from 1.2 to 2.0,
(7) a target for sputtering, which contains In, Sb, O and at least one element selected from the group consisting of Sn and Hf, and whose atomic ratio of Sb/In is from 1.2 to 2.0,
(8) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering a target (E) for sputtering, which contains in, Sb and O, and whose atomic ratio of Sb/In is from 1.2 to 2.0 (the process being hereinafter referred to as xe2x80x9cprocess-4xe2x80x9d),
(9) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering simultaneously:
(i) a target (E) for sputtering, which contains In. Sb and O, and whose atomic ratio of Sb/In is from 1.2 to 2.0, and
(ii) at least one target (C) for sputtering selected from the group consisting of Sn, SnO, Hf and HfO2 (the process being hereinafter referred to as xe2x80x9cprocess-5xe2x80x9d), and
(10) a process for producing an InSbO4-containing transparent electroconductive film, which comprises the step of sputtering a target (F) for sputtering, which contains In, Sb, O and at least one element selected from the group consisting Sn and Hf, and whose atomic ratio of Sb/In is from 1.2 to 2.0 (the process being hereinafter referred to as xe2x80x9cprocess-6xe2x80x9d).